[Raapys]

But the 'work = force * distance' function is fatally flawed when used in this situation, because the result of the equation will be zero, indicating no energy has been spent, no work has been done. Obviously this is completely incorrect, since you'll be standing there sweaty and tired, having wasted alot of energy on the task.

I think a fitting metaphor would be two guys pulling each side of a rope. They're both applying kinetic energy to the rope, but in different directions, canceling it out. So even if the rope isn't actually moving, there's still alot of work being done on it. The difference is that where both these two guys would eventually get tired, gravity does not.

Hmm, I guess one solution would be that the force you're using to hold the box up is simply being applied as kinetic energy to the *Earth*, thus seemingly 'disappearing' since it's hardly noticeable for something on that scale.